If you want to try the built-in text expansion for “free” (very limited compared to what one of the specialized apps can do, but useful for giving a taste of how it works), I think it's still under System Preferences -> Keyboard -> Text as of Sierra (I'm still on El Capitan at the moment).
I completely overlooked it as an option for years until some blogger mentioned it as an essential productivity tool, but it turned out to be pretty nice and useful for a lot more than I thought it would be.
As far as a word processor with an outline view goes, maybe you might try
Manuscripts? It's designed specially for academics writing research papers, so I don't know how applicable it might be for your own projects. But it's got a nice collapsible outline view for each section, and pre-formatted templates for submission to major journals, alongside other niceties such as importing citations, etc.
It's a little pricey for the full version which can make documents beyond 1500 words (free version makes as many as those as you want, and you get 3 free unlimited length docs as a trial), but every so often the developer has a deep-discount sale, usually around educational (they had a discount for Pi Day this March) and back to school times.